Cocaine has for a long time been, and remains, a commonly abused drug. In order to understand why cocaine users have a hard time stopping using the drug we have to get a better understanding of addiction. A newly developed self-administration procedure that causes rats to develop an increased motivation to self-administer cocaine will be used as an animal model to study the addictive process. Two factors appear to be important leading to an increased reinforcing efficacy of cocaine: round-the-clock access for at least 10 days and a forced deprivation or abstinence period. Using microdialysis the levels of dopamine and glutamate in the nucleus accumbens will be examined following a binge/abstinence protocol. These levels will be compared to levels following an acute cocaine challenge in a hope to find the neuroadaptations that take place in addiction.